The method of chemical-mechanical polishing (CMP) process is one of global planarization techniques which utilizes the mechanical manner by grinding material and the chemical manner by acid-base balance solution to partially remove surface portion of the wafer for globally planarizing the surface of the wafer so that the subsequent thin film deposition and etching processes can be implemented. Since the global planarization technique is a basic step of an inter-connection metallization process of the wafer and the CMP process is generally accepted feasible for globally planarizing the surface of the wafer, thus, the CMP process is widely used in the semiconductor process.
Conventionally, while performing the CMP process of the global planarization technique, the pressure distribution of the wafer is generated by the finite element method to evaluate the probable statuses of pressure field associated with the wafer. The distribution of relative velocity field on the wafer is made by a relative velocity formula which indicates the relative rotation speed between the wafer and arbitrary positions of the polishing pad. In another case, the relationship between the velocity field and the removal rate is created by experimental results associated with the wafer.
During the CMP process, the functions of the polishing pads includes: (1) uniformly spreading the slurry on the polished surface of the wafer; (2) removing the polished material away from the surface of the wafer; and (3) mechanically providing the wafer with the carrying platform. In fact, although it is quite complicated among mechanical, chemical, and physical effects while performing the CMP process, however, the material-removal rate (MRR) commonly dominates the result of the CMP process and MRR is described by Preston's formula: MRR=Cp×P×V, where “Cp” is Preston coefficient, “P” is down force or pressure, and “V” is the relative velocity of wafer to pad.
While polishing the wafer by a generic CMP process, the rotation direction and rotation speed of the wafer covered by the polishing pad are the same as these of the polishing pad and theoretically, the relative velocity of each position on the wafer is the same. In another case of compensation CMP process, the velocity field distribution of the wafer is not uniform because endpoint detection and polished amount saving of the pad need to be considered. No matter how the generic CMP process or the compensation CMP process is used to satisfy the functions (1) and (2) of the polishing pads in the above-mentioned description, a plurality of patterns and grooves must be formed on the polishing pad in the prior art.
However, while performing the generic CMP process having patterns and the compensation CMP process having different patterns and profiles, the practical polishing frequency and the number of polishing times on the polishing pads have errors in comparison to theoretical results of the pads. Further, these problems are still not solved. Consequently, there is a need to develop a novel method to solve the above-mentioned problems.